Electrical contact terminal



D. R. ZELL ETAL March 1, 1966 March 1, 1966 D. R. ZELL ETAL ELECTRICAL CONTACT TERMINAL 2 Sheets-Sheet 2 Filed Oct. 4, 1965 ice ' Patented Mar. 1, 1966 3,238,497 ELECTRICAL CONTACT TERMINAL Dale R. Zell, Elizabethtown, and John A. Zimmerman, Jr., Hershey, Pa., assignors to AMP Incorporated, Harrisburg, Pa.

Filed Oct. 4, 1963, Ser. No. 313,821 4 Claims. (Cl. 339252) This invention relates to disengageable electrical contact terminals of the pin and socket type.

In accordance with well-known prior art practice in the design of pin and socket type terminals, the contact pressure between the pin and socket is achieved by means of a separate spring mounted on the socket member which bears against the inserted pin and presses it against the internal wall of the socket. This method of establishing the contact pressure is satisfactory for relatively large contacts. However, where the contacts are intended for usage on fine wire, such as AWGZS and finer, is impractical to provide a separate contact spring because of the small size of the contacts. Accordingly, it is necessary to utilize alternative contact pressure generating devices on the smaller terminals.

It is an object of the present invention to provide an improved contact terminal of a type particularly intended for relatively fine wires. It is a further object of the invention to provide an improved stamped and formed contact pin which includes an integral contact pressure generating means. A further object is to provide a stamped and formed contact pin having an integral contact pressure applying means which is formed as part of the pin itself. A further object is to provide an extremely small contact terminal which is at the same time relatively durable and foolproof and is not susceptible to damage as a result of mishandling.

These and other objects of the invention are achieved in a preferred embodiment comprising a stamped and formed contact pin having a rolled cylindrical shank portion from one end of which an open-U type ferrule extends to facilitate attachment to a wire. A reduced diameter pin portion extends from the other end of the shank, this pin comprising two divergent semi-cylindrical sections which are integral with the shank and which are movable relatively towards each other until their edges are in abutting relationship to form a single cylindrical contact pin. The one semi-cylindrical section is relatively longer than the other section and has an end portion which is curved towards, and extends past the center line of the pin. The shorter section also has a laterally curved end which lies partially behind the curved end of the longer section, the arrangement being such that upon insertion of the pin into a cylindrical socket, the two semi-cylindrical sections are resiliently biased against each other by the socket thereby to establish the contact pressure between the mated terminals.

In the drawing:

FIGURE 1 is a perspective view of a contact pin in accordance with the invention.

FIGURE 2 is a perspective view of a complementary socket.

FIGURE 3 is a top plan view of the pin of FIG- URE 1.

FIGURE 4 is a fragmentary view showing a portion of a pair of connector blocks with a contact pin mounted in one of the blocks and a socket in the other block.

FIGURE 5 is a view similar to FIGURE 4 but showing the parts in engagement with each other.

FIGURE 6 is a plan View of the stamped blank from which the contact pin of FIGURE 1 is formed.

FIGURE 7 is a sectional view taken along the lines 7-7 of FIGURE 3.

FIGURE 8 is a frontal view of the contact pin.

Referring first to FIGURES 1 and 2, a pair of contact terminals in accordance with the invention comprise a contact pin 2 and a socket 4. The socket 2 has an intermediate cylindrical shank' portion 6 from one end of which a ferrule portion 8 extends Which is adapted to be crimped onto the end of a wire. Intermediate its ends within the shank portion, there is provided a reduced diameter section 10 forming a circumferential groove or recess in the shank which is cooperable with an insulating block to maintain the contact in the block.

A contact pin end 12 extends from the forward end of the shank which is composed of a pair of semi-cylindrical sections 14, 16. The section 14 is relatively longer than the section 16 and has a curved end which presents a forwardly facing spherical surface 18 when the pin is inserted into a contact socket. The relatively shorter arm 16 has an inwardly cupped .end 20 forming a spherical surface which lies behind the end 18 of the longer arm. The two semi-cylindrical sections 14, 16 do not normally abut each other but, in the preferred embodiment, each section diverges slightly with respect to the axis of the contact. tively towards each other when the pin end is inserted into a socket.

The pin 2 is advantageously formed by die-stamping and forming techniques, a convenient form of blank for this operation being shown in FIGURE 6. In this figure, the several parts of the pin contact are identified 'by the same reference numerals, differentiated by prime marks, as the finished pin contact in FIGURE 1. It will be noted that the two arms or extensions 14 and 16 are subsequently formed into the semi-cylindrical sections of the finished pin end. The arm 14 has a triangular tip 18 which is formed into a spherical surface while the end of the arm 16' is rounded. During forming, the shank forming portion 6 is first U-ed and then rolled to form the cylindrical shank 6 with the seam 22 extending along one side and lying in the plane which separates the two semi-cylindrical sections 14, 16 of the pin end. When the triangular tip 18' of arm 14' is formed into a spherical surface, its extreme end will extends toward the axis of the contact and will overlap the spherical surface 20 which is formed from the semicircular end 20' of the arm 16'. In the finished pin, then, the spherical ends of the two arms have overlapping surface portions which prevent entry of a foreign object along the contact axis from the front which would have the effect of wedging the arms apart. These overlapping spherical surfaces also facilitate entry of the pin end into a socket as is described more fully below.

The socket contact 4 is similarly formed by U-ing and rolling flat stock to produce a shank 24, a ferrule-forming end 26 which is adapted to be crimped onto a wire, and a socket end 30 which is separated from the shank by a reduced diameter section 28. As is explained more fully below, the contacts are advantageously formed from metal stock which is relatively thick when compared to the radii of the various parts such as the shanks, the socket 30, and the pin end. For this reason, the seams remain closed Without welding or soldering and the seam of the socket 30 will not be separated under the influence of the radially directed contact force of the pin.

Contacts of the type shown are commonly used in dielectric blocks as shown at 34 and 40 in FIGURES 4 and 5. The blocks 34, 40 may be of relatively firm material such as a firm polyurethane and are provided with cavities extending therethrough into which the pins are inserted. Each cavity has a slight construction as indicated which cooperates with the reduced diameter sections 10, 28 of the contacts for retention purposes.

Upon movement of the dielectric blocks towards each other from the position of FIGURE 4 to the position The two sections thus move rela-.

of FIGURE 5, the curved end 18 of the relatively longer section 14 first engages the flared or chamfered mouth of the socket. The inwardly curved end 20 of the short section 16 thereafter engages the mouth of the socket and the two semi-cylindrical sections are resiliently urged against each other to form a cylindrical contact pin which will bear against the internal wall of the socket for the entire portion inserted. The inherent tendency of the two semi-cylindrical sections of the pin to spring apart establishes the necessary contact pressure at the interface of the connection to achieve the required electrical performance.

A salient feature of the invention is that the contacts can be manufactured in the relatively small sizes which are required for wires in the range of AWG28-32 and finer. A contact socket for an AWG28 wire, for example, may have an overall length (including the crimped portion) of about 0.44" and will have an outside diameter of about 0.045". When the parts are of this approximate size, a relatively thick stock material is used; for example, brass stock of about 0.008" in thickness, so that when the ferrule is formed by rolling, the wall thickness will be about one-fifth of the overall diameter of the socket. The pin is formed of the same material in the instance cited and the pin end has an overall length of about 0.15". Thus, while the metal stock may appear to be relatively thin, a rigid and sturdy device results because of the extremely short length of the parts and the small radii of the shanks, the socket, and the pin end.

Other features of the disclosed pin which render it resistant to damage are the overlapping arrangement of the spherical ends of the arms 14, 16 and the fact that when these two arms or sections are flexed relatively towards each other, their edges move against each other to form a thick walled cylinder capable of withstanding extremely high unit stresses without distortion. The overlapping ends of the two sections prevent accidental entry of a foreign object between the arms such as would cause them to be wedged apart and assures that the two sections will move towards each other when the pin is inserted into a socket even if the pin is not perfectly aligned with the socket. The camming effect of the overlapping spherical ends will always function to bring the pin end and the socket into axial alignment during initial stages of insertion. The overlapping arrangement of the ends of the sections coupled with the relatively thick walls of the sections and the fact that they move against each other upon insertion results in a structure which is substantially as durable and as resistant to damage as a solid pin produced by screw machine methods from bar stock.

A noteworthy achievement of the disclosed form of contact pin is that the contact pressure (i.e., the pressure which urges the pin against the sidewalls of the socket and which therefore governs the efficacy of the electrical connection between the par-ts) is obtained from the pin itself rather than from a separate contact spring as is common practice in the prior art. The use of a separate spring in prior art practice was dictated by the fact that the material commonly used for pin and socket contacts, a hardened 70-30 brass, has a relatively low yield point and a low elastic modulus. The contact pressure requirements in pin and socket contacts is such that a con ventional spring of a hardened brass would not produce the required contact pressure because of the physical properties of the brass. It was, therefore, common to provide a separate spring of a high strength material having a relatively high elastic modulus, for example, beryllium copper or spring steel. The present invention obviates the need of such separate springs even if the pin is of a 7030 brass by virture of the pin design which utilizes the physical capabilities of the brass in a manner such that an adequate contact pressure is developed.

The principal structural feature of the pin which contributes to this result is the arrangement of the two sections 14, 16 and particularly the fact that both of these sections are flexed upon insertion of the pin into the socket. Neither section, when it is flexed, is required to undergo a severe deflection which would exceed the elastic limit of the material at the ends of the section.

Changes in construction will occur to those skilled in the art and various apparently different modifications and embodiments may be made without departing from the scope of the invention. The matter set forth in the foregoing description and accompanying drawings is offered by way of illustration only. The actual scope of the invention is intended to be defined in the following claims when viewed in their proper perspective against the prior art.

We claim:

1. A stamped and formed contact terminal comprising a generally cylindrical shank portion having a crimpable ferrule extending from one end thereof for crimping said terminal onto a wire, a contact pin extending from the other end of said shank, said pin comprising two semicylindrical sections each of which is integral with said shank, one of said sections being relatively longer than the other of said sections, said one section having an end which is curved laterally towards, and overlapping the end of, said other section, the other section diverging from said shank with respect to the axis of said terminal and having an end which is laterally curved towards said first section, said sections being movable relatively towards each other upon insertion of said pin end into a complementary contact socket to form a cylindrical pin exerting a radially directed contact force against the wall of said socket.

2. A stamped and formed contact terminal comprising a generally cylindrical shank portion having an open-U ferrule extending from one end thereof and having a contact pin extending from the other end thereof, said pin comprising two divergent semi-cylindrical sections integral with said shank, one of said sections being relatively longer than the other of said sections and having an inwardly curved end, said end overlapping, and disposed axially beyond, the end of said first section, said other section having an end which is inwardly curved towards said first section, said sections being resiliently movable relatively towards each other to form a cylindrical contact pin upon insertion thereof into a contact socket.

3. A stamped and formed contact terminal comprising a generally cylindrical shank portion having an open-U ferrule extending from one end thereof and having a contact pin extending from the other end thereof, said pin comprising two divergent semi-cylindrical sections integral with said shank, a first one of said sections being relatively longer than the other of said sections, said sections having spherically formed ends directed relatively towards the axis of said terminal, the spherically formed end of said first section having portions thereof which overlap the spherically formed end of said other section whereby, upon insertion of said contact pin into a complementary socket, said sections are cammed towards each other and urged against each other to form a cylindrical pin within said socket with the surface of said pin being resiliently urged radially against the internal wall of said socket.

4. A stamped and formed contact terminal comprising a generally cylindrical shank portion, means on said shank at one end thereof for securing said terminal to a conductor, said shank having a contact pin extending from the other end thereof, said pin comprising two divergent semi-cylindrical sections integral with said shank, one'of said sections being relatively longer than the other of said sections and having an inwardly curved end, said end overlapping, and disposed axially beyond, the end of said first section, said other section having an end which is inwardly curved towards said first section, said sections being resiliently movable relatively towards each other to form a cylindrical contact pin upon insertion thereof into a contact socket.

References Cited by the Examiner UNITED STATES PATENTS 1,738,709 12/1929 Jones 339-217 X 2,330,948 10/1943 Brand et a1. 339217 X 6 2,727,299 12/ 1955 Klumpp. 3,123,427 3/ 1964 Yopp 339-262 X FOREIGN PATENTS 352,210 8/ 1905 France. 893,028 1/ 1944 France. 241,785 10/1925 Great Britain. 463,781 4/ 1937 Great Britain.

JOSEPH D. SEERS, Primary Examiner. 

4. A STAMPED AND FORMED CONTACT TERMINAL COMPRISING A GENERALLY CYLINDRICAL SHANK PORTION, MEANS ON SAID SHANK AT ONE END THEREOF FOR SECURING SAID TERMINAL TO A CONDUCTOR, SAID SHANK HAVING A CONTACT PIN EXTENDING FROM THE OTHER END THEREOF, SAID PIN COMPRISING TWO DIVERGENT SEMI-CYLINDRICAL SECTIONS INTEGRAL WITH SAID SHANK, ONE OF SAID SECTIONS BEING RELATIVELY LONGER THAN THE OTHER OF SAID SECTIONS AND HAVING AN INWARDLY CURVED END, SAID END OVERLAPPING, AND DISPOSED AXIALLY BEYOND, THE END OF SAID FIRST SECTION, SAID OTHER SECTION HAVING AN END WHICH IS INWARDLY CURVED TOWARDS SAID FIRST SECTION, SAID SECTIONS BEING RESILIENTLY MOVABLE RELATIVELY TOWARDS EACH OTHER TO FORM A CYLINDRICAL CONTACT PIN UPON INSERTION THEREOF INTO A CONTACT SOCKET. 